1. Technical Field
The present invention relates to a filter unit, a liquid ejecting head, and a liquid ejecting apparatus. In particular, the invention relates to a filter unit through which an ink flows as a liquid, an ink jet recording head which ejects the ink, and an ink jet recording apparatus.
2. Related Art
An ink jet recording head which discharges ink droplets is a representative example of the liquid ejecting head which discharges liquid droplets. An ink jet recording head which includes, for example, a head main body which discharges ink droplets from a nozzle opening and a filter unit (a flow path member) which supplies an ink from an ink cartridge (a liquid storage member), in which the ink is stored, to the head main body is proposed (for example refer to JP-A-2013-159051).
The filter unit includes an ink flow path which includes a filter chamber in which a filter is disposed, and which removes bubbles and foreign matter contained in the ink by filtration. Specifically, the filter unit is provided with a first member and a second member, in each of which a flow path is formed. A concave portion which is open to the second member side is formed in the first member of the downstream side, and a filter is thermally welded so as to cover the flow path which communicates with the concave portion. The filter chamber is formed in the concave portion which is sealed by the second member of the upstream side. A wall surface which forms the filter chamber of the second member is a tapered portion with a diameter which widens toward the first member side.
In the filter unit, the initial filling of the ink is performed by sucking the ink from the flow path of the first member of the downstream side. When the filter chamber is simply formed to be wider than the flow path, the flow speed decreases in the proximity of the circumference of the filter chamber. Therefore, by forming the wall surface of the filter chamber of the second member in a tapered shape, the distance between the wall surface and the filter surface decreases toward the circumference; thus, the reduction in flow speed in the filter chamber is suppressed. Since the reduction in flow speed in the filter chamber is suppressed, it is possible to favorably discharge bubbles within the filter chamber.
However, when filling of the ink from the flow path of the second member of the upstream side is carried out with the ink being pressurized, a portion of the bubbles in the filter chamber does not pass through the filter and remains pushed against the edges of a tapered portion. There is a concern that, during the printing or the like, bubbles which remain in the filter chamber will pass through the filter, reach the head main body and cause nozzle clogging and discharge problems.
Note that, this problem is present not only in a filter unit through which the ink flows, an ink jet recording head which discharges the ink, and an ink jet recording apparatus including the ink jet recording head, but also in the same manner in a filter unit through which a liquid other than the ink flows, a liquid ejecting head which ejects the liquid and a liquid ejecting apparatus.